Gas-fired immersion heating apparatus



lNVENTOR.

mums: unswzv ATTORN Ef M. J. DEWEY GAS-FIRED IIIIIERSION HEATING APPARATUS Filed D90. 10, 1945 FIG.3.

" March 6, 1951 Patented Mar. 6, 1951 UNI-TED fsTAT ss PATE NT Y oFF-ic f GAS-FIRED IMMERSION HEATING APPARATUS V s u Maurice J. Dewey, Detroit, Mich.

implication; December 10,1945, Serial No. 634,008

2 Claims. (Cl. 126-360) The invention relates to gas-fired furnaces, and more particularly to gas-fired immersion heaters for economically heating liquids.

An object of the invention is to provide a compact arrangement of immersed heating flues having large Surface areas for increasing the transfer of heat from the burning gases to the liquid.

Another object is to provide an immersion heater with flues that may be more readily cleaned. I 7

These and other objects are attained by the apparatus hereinafter more fully described and illustrated in the accompanying drawings, wherein Figure 1 is a side view of a heating apparatus embodying the invention; 7

Figure 2 is a cross section on line 2-2 of Figure 1;

Figure 3 is a plan view partly in section of a modified form of apparatus;

Figure 4 is a cross section on line 4-4 of Figure 3;

Figure 5 is an enlarged cross section of a rectangular flue of modified form.

Referring to Figures 1 and 2, i0 is a tank for the liquid to be heated and i i is the heating unit comprisinga vertical cylindrical inlet conduit l2 and a similar outlet conduit [3. Each conduit has at the bottom thereof a rectangular header M and MA respectively between which extend two spaced rectangular flues it. Each flue has wide sid surfaces It and narrow edges ll.

A suction fan i8 is connected to the outlet conduit [3 and a gaseous fuel and air mixing device it. is connected to the inlet conduit 12, there being an electric igniter 28 for delivering a burning gaseous mixture into the inlet conduit where it is drawn by the suction'fan through the flues. Suitable automatic controls are described in my Patent No. 2,259,299, issued October 14, 1941.

The principal advantage of theconstruction, as above described, is that the rectangular flues form a large surface area in contact with the liquid compared to the volume of the flue passages, thus greatly increasing the transfer of heat from the burning gases to the liquid. Also the rectangular form of the flues facilitates the cleaning of the outer surfaces thereof after continued use. 7

In Figures 3 and 4, a modified form of immersion heater is shown. In this construction the tank 25 has 4 cylindrical tubes 28 extending lengthwise of the tank along the sides thereof.

These tubes have their inlet ends projecting through one end of the tank and at the opposite end are connected to a rectangular header'Z'l. A series of rectangular flues 28 extend lengthwise of the tank, being connected at one end to the header 2'! and at the other end to a second rectangular header 29 which in turn has an outlet pipe 30 projecting through the same end of the tank as the inlet ends of the tubes 26. Each of the tubes 26 is provided with a mixing and igniting device while the outlet pipe 30 is connected to a suction fan. In the modified construction as described, the rectangular flues 28 have the same advantage as in the first described 4 construction, in that they present a large surface area in contact with the liquid and are readily cleaned.

Also there is a further advantage when the rectangular flues are arranged, as shown, with their narrow edges in a horizontal plane and their wide sides in a Vertical plane, because this permits the circulating liquid in the tank to sweep against the sides and more rapidly extract the heat from the flues.

It will be understood that the invention also contemplates a construction as shown in Figures 1 and 2 wherein there are more than two flues l5 extending between the headers it and l lA and conversely wherein there is only a single flue between the headers.

In Figure 5 there is illustrated a rectangular flue [5A havinga series of fins 3| projecting inwardly from each of the side surfaces IBA. This greatly increases the metal surface contacting with the gases traveling through the flue and more quickly dissipates the heat of combustion to the side walls. It has been found that an interally finned construction of this type conducts the heat from the flue gases to the liquid in the tank so much more rapidly that the total length of flue may be greatly decreased while maintaining the sam efficiency as with a much longer rectangular flue without the fins.

What I claim as my invention is:

1. An immersion heater comprising a cylindrical inlet conduit adapted to extend into a liquid,

a gaseous fuel and air mixing device connected' outlet conduits and a series of rectangular flues extending between said headers, the cross section of each flue having one dimension substantially greater than the othenproviding parallel pasto form a large surface area compared .to the volume and in proximity to all ,DQIHQQ? .of the burning gas stream and to thereby increase the transfer of heat from the burning gases to the liquid.

MAURICE J. DEWEY.

REFERENCES CITED The following references are of record in the file of this patent:

'i iEs. P TENTS Number Name Date 1,630,309 Pitman May 31, 1927 2,172,953 Nelson Sept. 12, 1939 12,182,735 O'Dowd Dec. 5, 1939 2,226,816 Hepburn Dec. 31, 1940 2,244,800 Pascale June 10, 1941 2.299218 Turpin y 21, 1942 2,385,854 Woifersperger Oct. 2, 1945 

